This invention relates to window blinds. More particularly this invention relates to window blinds that can be rolled up and rolled down with a continuous or endless cord.
In the typical window blind, a plurality of sets of cords are used to roll the blinds up or down. Generally, one set of cords is used at each of several places vertically along the window blind. These sets of cords are connected to the material used to cover the window. The cords extend up into the headrail where they are guided to one end of the headrail. At the end of the headrail, the cords exit the headrail and hang along one edge of the window blind. Typically, at least two sets of these cords are used along the length of the window blind. For window blinds that cover wider windows, additional sets of cords may be used.
When the window blind is raised, the cords hanging at the end of the window blind are pulled downwardly, thereby causing the window covering material to be raised by the cords. The window blind is set in position by a locking mechanism which locks the cords hanging at the end of the window blind and thus the window covering material in the desired position. When the window blind is to be lowered, the cords are pulled to unlock the cords from the locking mechanism. The weight of the window covering material pulls down the cords thereby lowering the window covering material and simultaneously raising the cords at the end of the window blind. The cords and the window covering material can then be locked in place at the desired height, or the window covering material can be lowered to its full length.
Some blinds of this type have the lower end of the window covering material arranged so that when the cords are pulled to raise the material, it rolls up on itself. For example, the bottom of the window covering material might be affixed to spools along the length of the material. Although any type of material could be used, it is common for such blinds to be made of bamboo. Blinds of this type are referred to as roll up blinds.
One problem with such a typical window blind is that when the blind is raised, the cords hanging at one end of the window blind which are used to raise and lower the window blind reach a long length. In cases where the blinds are designed to cover a window of substantial height, these cords can be of substantial length and may accumulate on the floor. This is undesirable for safety as well as aesthetic reasons. People may trip over these long lengths of cords. Moreover, small children can become entangled in them, possibly becoming strangled.
Another problem with the typical window blind having more than one set of cords to raise and lower the window covering material is that it is difficult to maintain the window covering material horizontal when the blind is raised and lowered. If one or more sets of cords are not pulled downward or allowed to rise the same distance as the other sets of cords, one set of cords associated with one end of the window blind may be raised or lowered a greater distance than another set of cords associated with another end of the window blind. As a result, one end of the window blind may be raised or lowered a greater distance than the other end of the window blind.
Yet another problem with the typical roll up window blind arises when the window covering material is rolled up, after having been completely unrolled. In that situation, there is no way to control the direction in which the blind will roll up around itself.
If the window covering material rolls up toward the window, several undesirable effects follow. The physical configuration of the rolled up blind is aesthetically undesirable. The rolled up portion of the window covering material may make contact with the window and be forced inward. Also, contact against the window will increase the force required to raise the window covering material and the window covering material or one of the cords may catch on a window lock or other portion of the window, with potentially disastrous results. Further, where the window covering material is rolled up toward the window, the surface of the window covering material facing the room ("the interior surface") would be exposed to the sun while in a rolled up position, with resulting fading. Over time, this interior surface would develop horizontal lines of lighter and darker material, assuming that the blind were left in various partially rolled-up configurations.
Another type of roll up blind utilizes a continuous or endless cord to rotate a rod, around which the window covering material is connected. As the rod is rotated by means of a roll up cord, the window covering material either wraps around or unwraps from the rod, depending upon which way the rod is rotated. One problem with this type of a roll up blind is that, if the roll up cord is continually pulled, the rod will continue to rotate even when the window covering material is either completely rolled up or down. This causes the window covering material to roll up in the wrong direction after it has been completely rolled down, creating an unsightly appearance. On the other hand, if the window covering material has been completely rolled up, the window covering material will just continue to roll up on itself.
It would be desirable to provide a window blind that does not yield a long length of cord when the blind is rolled up.
It would also be desirable to provide a window blind with window covering material that remains substantially horizontal when the window blind is raised and lowered.
It would further be desirable to provide a roll up window blind with window covering material that always rolls up in the same direction on the internal surface of the material.